Led lighting systems

ABSTRACT

Light fixture systems and application of ambient light measurement for improving lighting system efficiency.

RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 61/599,037, filed Feb. 15, 2012, which is incorporatedin its entirety herein by reference.

BACKGROUND

Existing systems for setting or resetting operating parameters of lightfixtures are ineffective. It is difficult to commission/install lightfixtures so they operate efficiently because ambient light levels at theinstall site are difficult to predict. In addition, it is also difficultto acquire accurate ambient light measurements during and afterinstallation.

SUMMARY

The technology described herein relates to setting or resettingoperating parameters of light fixture systems. One implementation is amethod for controlling light emitting diode (LED) light fixtures. Themethod includes monitoring a clock source signal to identify thepresence of a feature in the clock source signal. The method alsoincludes generating a trigger signal with a triggering module inresponse to identifying the presence of the feature in the clock sourcesignal. The method also includes providing the trigger signal to each ofa plurality of light fixtures to command each of the plurality of lightfixtures to stop outputting light. The method also includes measuringambient light with a light sensor located with the plurality of lightfixtures.

In some embodiments, the clock source signal is an alternating voltagesignal, and wherein the feature in the clock source signal is theoccurrence of a zero-crossing in the alternating voltage signal. In someembodiments, the triggering commands each of the plurality of lightfixtures to stop outputting light for a predefined time period. In someembodiments, an ambient light monitor measures the ambient light inresponse to the trigger signal.

In some embodiments, the clock source signal is: an AC or DC signal alsoused to provide power to the plurality of light fixtures, a power linecommunication signal carried by an AC or DC signal used to provide powerto the plurality of light fixtures, or a signal transmitted by a clocksource generator that generates the clock source signal. In someembodiments, the ambient light is measured using one or more lightemitting diodes in the one or more of the plurality of light fixtures.In some embodiments, the method includes varying operating parameters ofone or more of the light fixtures based on the measured ambient light.

Another implementation is a light fixture control system that includes amonitoring module that monitors a clock source signal to identify thepresence of a feature in the clock source signal. The system alsoincludes a triggering module that generates a trigger signal in responseto identifying the presence of the feature in the clock source signal.The system also includes a command module that provides the triggersignal to each of a plurality of light fixtures to command each of theplurality of light fixtures to stop outputting light. The system alsoincludes a ambient light module that monitors ambient light measured inproximity to the plurality of light fixtures.

In some embodiments, the clock source signal is an alternating voltagesignal, and wherein the feature in the clock source signal is theoccurrence of a zero-crossing in the alternating voltage signal. In someembodiments, the command module commands each of the plurality of lightfixtures to stop outputting light for a predefined time period. In someembodiments, the ambient light module measures the ambient light inresponse to the trigger signal. In some embodiments, the clock sourcesignal is: an AC or DC signal also used to provide power to theplurality of light fixtures, a power line communication signal carriedby an AC or DC signal used to provide power to the plurality of lightfixtures, or a signal transmitted by a clock source generator thatgenerates the clock source signal.

In some embodiments, the ambient light is measured using one or morelight emitting diodes in the one or more of the plurality of lightfixtures. In some embodiments, a light fixture control module variesoperating parameters of one or more of the light fixtures based on themeasured ambient light.

Another implementation is a method for commissioning a lighting system.The lighting system including a plurality of light fixtures, and aplurality of light sensors, where a light sensor from the plurality oflight sensors is assigned to each light fixture. The method includesmeasuring ambient light with the light sensor assigned to each lightfixture. The method also includes designating each light fixture to alighting group based on the ambient light measured with the light sensorassigned to each fixture.

In some embodiments, the method includes acquiring an updatedmeasurement of ambient light with the light sensors assigned to eachlight fixture and designating each light fixture to a new lighting groupbased on the updated ambient light measurements. In some embodiments,the light sensors assigned to each light fixture include one or morelight emitting diodes in the light fixture to measure the ambient light.In some embodiments, a unique light sensor is assigned to each lightfixture.

In some embodiments, a light sensor is assigned to more than one lightfixture. In some embodiments, the method also includes, prior tomeasuring ambient light with the light sensor assigned to each lightfixture, monitoring a clock source signal to identify the presence of afeature in the clock source signal, and generating a trigger signal witha triggering module in response to identifying the presence of thefeature in the clock source signal, and providing the trigger signal toeach of the plurality of light fixtures to command each of the pluralityof light fixtures to stop outputting light.

In some embodiments, the method includes making a plurality ofmeasurements of ambient light over a period of time with the lightsensor assigned to each fixture and modifying light fixture groupdesignations based on the plurality of ambient light measurements. Insome embodiments, the method includes assigning one or more of the lightsensors to a different light fixture based on the ambient lightmeasurements.

Another implementation is a lighting system commissioning apparatus. Thelighting system including a plurality of light fixtures, and a pluralityof light sensors, where a light sensor from the plurality of lightsensors is assigned to each light fixture. The apparatus includes anambient light module configured to measure ambient light with the lightsensor assigned to each light fixture and a commissioning moduleconfigured to designate each light fixture to a lighting group based onthe ambient light measured with the light sensor assigned to eachfixture.

In some embodiments, the ambient light module is configured to acquirean updated measurement of ambient light with the light sensors assignedto each light fixture, and the commissioning module is configured todesignate each light fixture to a new lighting group based on theupdated ambient light measurements. In some embodiments, the lightsensors assigned to each light fixture include one or more lightemitting diodes in the light fixture to measure the ambient light. Insome embodiments, a unique light sensor is assigned to each lightfixture. In some embodiments, a light sensor is assigned to more thanone light fixture.

In some embodiments, a monitoring module, a triggering module, and acommand module. Prior to measuring ambient light with the light sensorassigned to each light fixture, the monitoring module monitors a clocksource signal to identify the presence of a feature in the clock sourcesignal, the triggering module generates a trigger signal in response toidentifying the presence of the feature in the clock source signal, andthe command module provides the trigger signal to each of a plurality oflight fixtures to command each of the plurality of light fixtures tostop outputting light.

Another implementation is a method for commissioning a lighting system.The lighting system including a plurality of light fixtures. The methodincludes measuring ambient light with a light sensor located with theplurality of light fixtures. The method also includes designating one ormore of the plurality of light fixtures to a first lighting group basedon the measured ambient light.

Another implementation is a method for grouping light fixture in alighting system. The method includes assigning a light sensor to eachlight fixture in the lighting system. The method also includes measuringambient light with the light sensor assigned to each light fixture overa period of time. The method also includes designating each lightfixture to a lighting group based on the ambient light measured with thelight sensor assigned to each fixture.

Another implementation is a method for calibrating an LED light fixturethat includes generating a reference light output from a light source.The method also includes measuring the reference light output from thelight source by using at least one LED in the light fixture as a lightsensor. The method also includes determining a calibration value bycomparing the reference light output measurement to a reference value,such that by application of the calibration value to the operation ofthe LED light fixture, the LED light fixture will operate havingproperties associated with the reference value.

In some embodiments, the method includes the calibration value in amemory associated with the LED light fixture. In some embodiments, themethod includes placing the light source and LED light fixture in anenclosure and, in the absence of ambient light, generating the referencelight output and measuring the reference light output. In someembodiments, measuring the reference light output from the light sourceincludes measuring the reference light output using the plurality ofLEDs in the light fixture as light sensors, wherein each LED of theplurality of LEDs acquires a different reference light outputmeasurement.

In some embodiments, the method includes determining a calibration valuefor each LED in the LED light fixture by comparing the reference lightoutput measurement of each LED to a reference value. In someembodiments, the method includes storing each LED's calibration value ina memory associated with the LED light fixture. In some embodiments, byapplication of the calibration value to the operation of the LED lightfixture, the LED light fixture will sense light having propertiesassociated with the reference value.

In some embodiments, measuring the reference light output from the lightsource includes measuring the reference light output using the pluralityof LEDs in the light fixture as light sensors, wherein the plurality ofLEDs is configured as a string of LEDS to acquire the light outputmeasurement.

Another implementation is an LED light fixture calibration system thatincludes a light source to generate a reference light output. The systemalso includes a calibration module coupled to the light source and anLED light fixture, wherein the calibration module measures the referencelight output from the light source by using at least one LED in thelight fixture as a light sensor and, wherein the calibration moduledetermines a calibration value by comparing the reference light outputmeasurement to a reference value, such that by application of thecalibration value to the operation of the LED light fixture, the LEDlight fixture will operate having properties associated with thereference value.

In some embodiments, the system includes a processor for storing thecalibration value in a memory associated with the LED light fixture. Insome embodiments, the system includes an enclosure in which the lightsource and LED light fixture are placed and, in the absence of ambientlight, the light source generates the reference light output and the LEDlight fixture measures the reference light output.

In some embodiments, the LED light fixture has a plurality of LEDS andthe LEDs measure the reference light output using the plurality of LEDsin the light fixture as light sensors, wherein each LED of the pluralityof LEDs acquires a different reference light output measurement. In someembodiments, the calibration module determines a calibration value foreach LED in the LED light fixture by comparing the reference lightoutput measurement of each LED to a reference value. In someembodiments, the processor stores each LED's calibration value in amemory associated with the LED light fixture.

In some embodiments, by application of the calibration value to theoperation of the LED light fixture, the LED light fixture will senselight having properties associated with the reference value. In someembodiments, measuring the reference light output from the light sourceincludes measuring the reference light output using the plurality ofLEDs in the light fixture as light sensors, wherein the plurality ofLEDs is configured as a string of LEDS to acquire the light outputmeasurement.

The lighting systems described relate broadly to installation,calibration, operation, measurement of lighting fixtures. Someembodiments include the use of LED's as light sources and as lightsensors. The light fixture control systems described herein (hereinreferred to as “technology”) can provide one or more of the followingadvantages. One advantage of the technology is that light sensors(including LEDs in a light fixture) can accurately measure ambient lightlevels at the install/operational site because the light fixtures at thesite are synchronized so the fixtures are in an off-state at the sametime. Another advantage of the technology is that light fixtures can begrouped and/or regrouped to vary or optimize system efficiency byaccounting for varying ambient light levels in proximity to the lightfixtures. Another advantage of the technology is that light fixturesystems can be operated more efficiently by employing calibration (e.g.,manual or automatic) techniques that account for variations in theperformance characteristics of the light fixtures (e.g., due tomanufacturing, system configuration, aging). Another advantage of thetechnology is that it solves a problem of having to have separateambient light sensors in your lighting system, or having to haveseparate modules on your fixture. This gives you the same amount ofperformance and flexibility without any of the added cost or complexity.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages will beapparent from the following more particular description of theembodiments, as illustrated in the accompanying drawings in which likereference characters refer to the same parts throughout the differentviews. The drawings are not necessarily to scale, emphasis instead beingplaced upon illustrating the principles of the embodiments.

FIG. 1 is a block diagram of a light fixture control system forsynchronizing a plurality of light fixtures and for measuring ambientlight, according to an illustrative embodiment.

FIG. 2 is a diagram of a process for controlling light fixtures,according to an illustrative embodiment.

FIG. 3 is a block diagram of a light fixture control system forsynchronizing a plurality of light fixtures and for measuring ambientlight, according to another illustrative embodiment.

FIG. 4A is a graphical representation of a waveform used as a clocksource signal for commanding light fixtures to stop outputting light,according to an illustrative embodiment.

FIG. 4B is a graphical representation of a waveform used to providepower to light fixtures and used as a clock source signal, according toan illustrative embodiment.

FIG. 5A is a functional block diagram of an embodiment of a powerlinecommunication control system for LED lighting fixtures, according to anillustrative embodiment.

FIG. 5B is a functional block diagram of an embodiment of a mastercontroller of a powerline communication control system for LED lightingfixtures, according to an illustrative embodiment.

FIG. 5C is a functional block diagram of an embodiment of a slave LEDlighting fixture unit of a powerline communication control system forLED lighting fixtures, according to an illustrative embodiment.

FIG. 6A is a block diagram of a portion of a lighting system, accordingto an illustrative embodiment.

FIG. 6B is a schematic illustration of duty cycles used to operate anLED fixture, according to an illustrative embodiment.

FIG. 6C a schematic illustration of a circuit used to measure voltageacross a string of LEDs that are used as light sensors, according to anillustrative embodiment.

FIG. 6D is a schematic illustration of a circuit used to measure voltageacross a string of LEDs that are used as light sensors, according to anillustrative embodiment

FIG. 6E is a schematic illustration of another circuit used to measurevoltage across a string of LEDs that are used as light sensors,according to an illustrative embodiment.

FIG. 7 is a block diagram of a clock source generator, according to anillustrative embodiment.

FIG. 8A is block diagram of a lighting system commissioning system,according to an illustrative embodiment.

FIG. 8B is block diagram of a lighting system commissioning system,according to another illustrative embodiment.

FIG. 9A is a schematic illustration of a light fixture grouping of lightfixtures in a lighting system, according to an illustrative embodiment.

FIG. 9B is a schematic illustration of an alternative light fixturegrouping for the lighting system of FIG. 9A.

FIG. 10 is a schematic illustration of components of an LED lightfixture, according to an illustrative embodiment.

FIG. 11 is a schematic illustration of an LED light fixture calibrationsystem, according to an illustrative embodiment.

FIG. 12 is a flowchart of a method for calibrating an LED light fixture,according to an illustrative embodiment.

FIG. 13 is a schematic illustration of an LED light fixture calibrationsystem, according to an illustrative embodiment.

DETAILED DESCRIPTION

Ambient light sensors may be used to save energy, and dim lightingsystems to a lower light level when ample ambient light is present in aparticular space. The challenges with any ambient light sensor in alighting environment, whether it be an office, classroom, or atrium, isthat an ambient light sensor not only picks up ambient light (i.e.,natural light), but also any light contributed by any active lightfixture or light source in proximity to the ambient light sensor. Insome embodiments it is desirable to synchronize the operation of lightfixtures (or separate controllable units inside a single light fixture)so that the light fixtures are all off at the same time. This allows fortrue, natural ambient light to be measured in the space.

An example of a typical conventional LED fixture install involves usingdaylight harvesting/ambient light sensors in a lighting system in aclassroom setting. This lighting system would use linear or panellighting as general illumination and also include 1 or 2 ambient lightsensors in the room to measure the ambient light, and dim the fixturesas needed to a minimum level to maintain a certain candela distribution.The less ambient light available, the more intensity the light fixtureswill produce to provide the necessary light levels. Problems with thistype of system include:

-   -   Ambient light sensors need to be sourced, adding another        component to the lighting plan, adding cost and integration        understanding. Usually the sensor manufacturer is different than        the light fixture manufacturer.    -   Determining where to locate the ambient light sensor can be        difficult depending on the classroom layout and available        natural light levels. This can prove troublesome during the        installation process.    -   Compatibility of fixtures and ambient light sensors. Trying to        guarantee compatibility of the two can be troublesome.

FIG. 1 is a block diagram of a lighting environment 100 of a lightfixture control system 102 for synchronizing a plurality of lightfixtures 104A, 104B . . . 104N (generally 104) and for measuring ambientlight, according to an illustrative embodiment. The environment 100 alsoincludes a light sensor 106 that measures light (e.g., ambient light) inthe proximity of the light fixtures 104. Exemplary light sensors thatcan be used include, for example, model LX1972A and model LX1973B lightsensors sold by Microsemi Corporation (Aliso Viejo, Calif.), modelTSL4531 digital ambient light sensor sold by ams AG (Austria), the ADCfamily of light sensors sold by Sensor Switch, Inc. (Wallingford,Conn.), and the FS-155 and FS-155-1 model occupancy sensors sold byWattStopper (Santa Clara, Calif.). In some embodiments, a separate lightsensor device (e.g., one of the Microsemi or ams light sensors) is notused to make ambient light measurements. Rather, one or more LEDs in anLED light fixture of the system are used. As described further herein(e.g., with respect to FIG. 6A), the LEDs of a light fixture can be usedas photodiodes because they are sensitive to incoming electromagneticenergy to which they are exposed.

Each light fixture 104 includes two LED lights (LED1 and LED2). The LEDlights can be the same LED type or different LED types. For example, inone embodiment, LED1 is a white LED with a 2700K color temperature andLED2 is a white LED with a 6000K color temperature. Alternative numbers,types (e.g., color, color temperature), and different combinations ofLEDs can be used in alternative embodiments.

In operation, an input device 108 (e.g., a dimmer) connected to thelight fixture control system 102 is used by an operator to control theoutput of the light fixtures 104. In this embodiment, the output ofdevice 108 specifies what color temperature of light within the range of2700K to 6000K the user wants the light fixtures 104 to output. Table 1provides exemplary values for the output voltage of the device 108. Thesystem 102 also includes a light fixture control module 112 that outputsa PWM signal to control the light fixtures 104 based on the output ofdevice 108. Table 1 also lists the PWM signal that the light fixturecontrol module 112 outputs, and the color temperature that the lightfixtures 104 output based on the PWM signal. One skilled in the art willappreciate that intermediate voltage levels (e.g., voltage between 1.0and 4.5 volts) will produce light having a color temperature between2700 K and 4350 K).

TABLE 1 Exemplary values for light fixture operation Light fixturecontrol module Dimmer voltage (PWM duty cycle command) to Light outputoutput two different LED types color temperature 0.0 volts LED1 (0% dutycycle) No light LED2 (0% duty cycle) 1.0 volts LED1 (100% duty cycle)2700 K LED2 (0% duty cycle) 4.5 volts LED1 (50% duty cycle) 4350 K LED2(50% duty cycle) 10.0 volts  LED1 (0% duty cycle) 6000 K LED2 (100% dutycycle)

The light fixture control system 102 also includes a monitoring module116, a triggering module 120, a command module 124, an ambient lightmodule 128, and a clock source generator 132. FIG. 2 is a diagram 200 ofa process for controlling light fixtures, for example, the lightfixtures 104 of FIG. 1. The clock source generator 132 generates a clocksource signal (step 204) that is used by the system 102 to synchronizethe light fixtures 104. The monitoring module 116 monitors the clocksource signal to identify (step 208) the presence of a feature in theclock source signal (as described, for example, below).

The triggering module 120 generates a trigger signal (step 212) inresponse to identifying the presence of the feature in the clock sourcesignal. The command module 124 provides the trigger signal (step 216 a)to each of the light fixtures 104 to command each of the light fixtures104 to stop outputting light. The command module 124 also provides thetrigger signal (step 216 b) to the ambient light module 128. The ambientlight module 128 measures the ambient light (step 220), in response tothe trigger signal, using for example, the light sensor 106 of FIG. 1.The ambient light module 128 then outputs an ambient light measurementsignal (step 224) to the light fixture control module 112.

In some embodiments, the light fixture control module 112 variesoperating parameters of one or more of the light fixtures 104 based onthe measured ambient light. In some embodiments, the light fixturecontrol module 112 decreases the illumination intensity of one or moreof the light fixtures 104 when the measured ambient light is relativelyhigh (e.g., mid-day when light from the sun entering the space isrelatively strong in the vicinity of the light fixtures). The lightfixture control module 112 may vary operating parameters based onexpected changes to the ambient light. For example, the system mightdecrease illumination levels at night when it is typical that peoplewill not be in the lighting environment. Another example is that itmight be desirable to change the color temperature of the fixturesdepending on the ambient light levels throughout the day. Depending onthe ambient light throughout the day, it might be desirable to changecolor temperature to change moods, or mimic and follow the natural colortemperature tendencies of daylight.

Other scenarios are calendar and time clock based, where certain lightlevels are maintained at certain times of day and altered accordingly.An example of this is in an office building setting. The office buildingmay lower light levels and power usage at 5:30 PM when the buildingbecomes unoccupied. But, the building has a time-stamped control modulethat will increase light levels at say 9 PM-10 PM, when the cleaningcrews are occupying the space. Another example is meeting spaces in abuilding. Using a time-stamped control module that is integrated to acomputer calendaring system, fixtures in meeting rooms could turn on andoff based on occupancy, but also whether the rooms are reserved or notfor meetings. Occupancy sensing and control is another example. Anadditional example would be classroom and meeting room control oflighting based on projector or TV use. Different light sensors canmeasure the ambient light and automatically control fixtures dependingif a projector is used (e.g., keep lights on at the back of the room,but dim the front).

FIG. 3 is a block diagram of another lighting environment 300 of a lightfixture control system 302 for synchronizing a plurality of lightfixtures 304A, 304B . . . 304N (generally 304) and for measuring ambientlight. The environment 300 also includes a light sensor 106 thatmeasures light (e.g., ambient light) in the proximity of the lightfixtures 304. The light fixture control system 302 includes lightfixture control module 112, ambient light module 128, and clock sourcegenerator 132 (e.g., the same modules as used in FIG. 1). In thisembodiment, as opposed to the embodiment of FIG. 1, each of the lightfixtures 304 includes a monitoring module 316, triggering module 320,and command module 324. Each of the modules (316, 320, and 324) performsthe same function as the same-named modules 116, 120, and 124 of FIG. 1;however, the functions are performed within (or part of) each lightfixture in the embodiment illustrated in FIG. 3.

FIG. 4A is a graphical representation of an AC signal waveform 404 usedas a clock source signal for commanding light fixtures to stopoutputting light. The AC signal waveform could supply power to the lightfixture and also includes a sine wave 414 that rides the sine wave ofthe AC signal waveform 404. In one embodiment, a monitoring module(e.g., monitoring module 116 of FIG. 1) monitors the waveform 404. Whenthe monitoring module 116 identifies the presence of a zero-crossing 408feature in the waveform, the triggering module 120 generates a triggersignal. The trigger signal is provided to the command module 124. Thecommand module provides the trigger signal to the light fixtures 104 tocommand the fixtures to enter a state in which the light fixtures 104stop outputting light. In some embodiments, the command module 124commands the light fixtures 104 to stop outputting light for apredefined time period (e.g., 1 ms, 5 ms, 10 ms, 1% of the duty cycle ofthe signal used to provide power to the light fixtures). In someembodiments, the waveform 404 also provides power to the plurality oflight fixtures 104 to cause the fixtures to illuminate.

FIG. 4B is a graphical representation of a DC signal waveform 412 usedto provide power to the plurality of light fixtures 104 and used as aclock source signal. In this embodiment, a power line communicationsignal 416 is carried by the DC signal 412. The power line communicationsignal 416 also acts as the clock source signal. When the monitoringmodule 116 identifies a particular pre-defined feature in the power linecommunication signal 416 (e.g., a particular encoded frequency), thetriggering module 120 responds to the identification of the feature bygenerating the trigger signal. The trigger signal is used by the systemto command the light fixtures 104 to stop outputting light and tocommand the ambient light module 124 to measure ambient light inproximity to the light fixtures 104.

One way to sync up fixtures involves doing so with the fixtures allbeing in an off state at the same time. The microprocessor reads theambient light when the fixture is off. One of the challenges is thatwhile that particular fixture is off, other surrounding fixtures willmost likely being in the “on” state (or “off” state), as themicroprocessors that are on each individual fixture have no way ofsyncing their PWMs to know that they will always be “off” at the sametime. To make this invention better, we can use power linecommunication, and the 50-60 Hz signal that goes along with it, as a wayto sync up all the fixtures on the power line communication network toensure their PWMs are in sync. By syncing up all of the fixtures on anetwork, when a fixture reads the ambient light coming from the LEDs inthe off state, it is the true ambient light measured because allfixtures will be off and not emitting light when the measurement ismade. The method involves using the zero cross signal of the AC linesupplied to the light fixtures as the synchronizing signal for aligningthe PWM signals for the fixtures.

Another implementation involves using the powerline communication as aclock source to sync the fixtures together. Powerline communicationsystems, often called powerline carrier communication systems, involvemethods that enable systems to carry data on a conductor that is alsoused for electric power transmission, such as a conventional 117 volt ACline, a 230 volt AC line (such as used in Europe), a 100 volt AC line(such as used in Japan), a 277 volt AC line (such as used in certaincommercial applications in the United States) or a 347 volt AC line(such as used in certain commercial applications in the Canada). Thereare many different ways to communicate on a powerline, but ultimatelyall communication is done by impressing a modulated carrier signal ontothe system power conductors together with the 117 volt AC power signaland separating the power signal and the communications signals at areceiving point.

In one embodiment, a powerline communication control unit is used withthe technology described herein and includes a master controller thatincludes a lighting control command processor for receiving a lightingunit control input from a lighting controller and generatingcorresponding lighting unit command outputs in a lighting system commandformat and a power distribution system interface connected to a powerdistribution system for superimposing the lighting unit command outputsonto the power distribution system and a power signal present thereon asa lighting command signal according to a lighting unit commandtransmission mode. This powerline communication technology isimplemented according to a modulation selected from the group consistingof: amplitude modulation; frequency modulation; phase modulation; binaryphase shift keying modulation; quadrature phase shift keying modulation;quadrature amplitude modulation; frequency shift keying modulation;phase shift keying modulation; and combinations thereof. Additionaldetail regarding power line communication systems and methods that canbe used with the technology in this disclosure are provided in AppendixA (attached here and incorporated by reference in its entirety).

Implementation of powerline communication techniques enables the systemto make sure the clock signal is used to set the operation of thefixtures to have their PWM signal in the off state at the same time.This enables the system to measure the ambient light in that fixturespace as true ambient light because all the light fixtures are commandedto be off at the same time. One of the advantages to this method is itcan be much faster than if the zero cross detection method was used. Aprogrammable logic controller (PLC) in the light fixture system cantransmit under normal operations at between 100 kHz-150 kHz. This ismuch faster than a 50 or 60 Hz signal corresponding to the zero crossdetection of the AC supply.

Referring to FIG. 5A, a block diagram of a powerline communicationcontrol system 10 for LED lighting fixtures is shown therein. Asillustrated, a powerline communication control system 10 of the presentinvention includes a conventional power distribution system 12, such asa 117 volt AC network, at least one master controller 14 and one or moreLED fixture slave units 16 (three of which are diagrammatically shown inFIG. 5A but it is to be appreciated that the amount of the slave units16 can vary depending upon the particular application). The controloutput 14A, from each master controller 14, is connected via the powerdistribution system 12, so as supply a separate control input to atleast one, and more preferably a plurality, of the slave unit 16

Referring first to an exemplary master controller 14 is coupled to oneor more conventional dimmer controllers 18 (four of which arediagrammatically shown in FIG. 5A but it is to be appreciated that theamount of the dimmer controllers 18 can vary depending upon theparticular application). Each master controller 14 receives one or moredimmer control inputs 18A from one or more of the conventional dimmercontrollers 18. It is to be appreciated that the dimmer controller 18may include, for example, a Digital Multiplex (DMX) controller(s), a0-10V Dimmer(s), a TRIAC dimmer(s) or an Electronic Low Voltage (ELV)Dimmer(s) and the dimmer control inputs 18A are conventional, standardoutput control signals of the corresponding types of dimmer controllers18. More generally, any conventional electrical controller can beaccommodated by providing a suitable interface for obtaining acontroller setting. Other controllers include current loop controllersas commonly used in the industrial process control of instruments. Onesuch class of controllers is known as 4-20 mA controllers.

The master controller 14, upon receipt of the dimmer control inputs 18A,first converts the conventional, standard control input or inputs 18Afrom the one or more master controllers 18 into corresponding powerlinecontrol signals 14A. Next, the master controller 14 imposes thepowerline control signals 14A onto the wiring of the power distributionsystem 12, together with the conventional power signal 12P present onpower distribution system 12, and also transmits the powerline controlsignals 14A through the power distribution system 12 to each one of theslave units 16. In a presently preferred embodiment of the presentinvention, the powerline control signals 14A may be, for example, in theform of a frequency shift keyed signal (FSK), a differential frequencysignal (DFSK) or a differential phase shift keyed signal (DPSK). Thecommand code format of the powerline control signals 14A may, forexample, be that of a commercially available controller format or aversion thereof modified for the specific needs of a powerlinecommunication control system 10 or may be designed specific for thepowerline communication control system 10.

According to the present invention, the powerline control signal 14A maybe in the form of broadcast commands to all of the slave units 16connected with the power distribution system 12, so that all slave units16 are controlled concurrently and in parallel with one another.Alternately, the powerline control signals 14A may be specificallyaddressed to an individual slave unit 16, or to groups of the slaveunits 16, thereby allowing individualized control of one or more of theslave units 16 of the powerline communication control system 10.

Next referring to an exemplary slave unit 16, as illustrated in FIG. 5A,the slave unit 16 includes one or more LED lighting units 16L (onlythree of which are diagrammatically shown in FIG. 5A but it is to beappreciated that the amount of the LED lighting units 16L can varydepending upon the particular application) and a communication and powersupply node 16A. As indicated, each communication and power supply node16A has a power and control input 16BA, 16BP which is connected with thepower distribution system 12 in order to receive both the powerlinecontrol signals 14A and the power signal 12P from the power distributionsystem 12. As indicated in FIG. 5A, the communication and power supplynode 16A, of each slave unit 16, initially separates the receivedpowerline control signals 14A from the received power signal 12P, andthen generates a DC power output 16P from the power signal 12P, and thensupplies the generated DC power signal 16P to the lighting units 16L inorder to power the lighting units 16L as controlled by the mastercontroller 14. The communication and power supply node 16A, of eachslave unit 16, also decodes the received powerline control signals 14Aand, in turn, then generates corresponding lighting control commands 16Cand subsequently supplies the control commands 16C to the lighting units16L so as to control the operation of the lighting units 16L.

Referring next to FIGS. 5B and 5C, more detailed block diagrams of boththe master controller 14 and the slave unit 16, according to the presentinvention, are respectively shown therein. As illustrated in FIG. 5A,each master controller 14 includes one or more dimmer control conversioncircuits 14B for converting the control inputs 18A, from thecorresponding dimmer controllers 18, into the corresponding dimmercommand inputs 14C to a microprocessor 14D which, under control of atleast one program(s) residing in a resident memory (not shown forpurposes of clarity) to generate the corresponding powerline controlsignals 14A, which are then superimposed onto the wires of the powerdistribution system 12 and the power signal 12P present thereon by apowerline interface 14E for transmission of the slave units 16. Asindicated, each master controller 14 will also include other necessarycircuitry, such as a power supply 14F for receiving electrical powerfrom the power distribution system 12.

Referring to FIG. 5C, the power and control input 16B of eachcommunication and power supply node 16A of each slave unit 16 includes acontrol input 16BA, connected to the power distribution system 12 and tothe input of a communication interface 16B which receives the powerlinecontrol signals 14A and the power signal 12P from the power distributionsystem 12, separates the powerline control signals 14A from the powersignal 12P, and provides corresponding control signals 14A to an inputof a slave control microprocessor 160. The slave control microprocessor160, operating under control of at least one program(s) residing in amemory (not shown for purposes of clarity), in turn, decodes controlsignals 14A and generates corresponding slave control signals 16E, whichare converted into corresponding analog or digital lighting controlcommands 16C, by a fixture interface 16F, and then communicated to eachone of the lighting units 16L.

A power input 16BP is likewise connected to the power distributionsystem 12 to receive the power signal 12 with the superimposed powerlinecontrol signals 14A and is connected to the input of a power supply 16Gwhich, in turn, generates DC power outputs 16P which are supplied to thecircuits of the communication and power supply node 16A and eventuallyto the lighting units 16L of the slave unit 16.

FIG. 6A is a block diagram of a portion of a lighting system 600,according to an illustrative embodiment. In this embodiment, the LEDs604 of the light fixture 608 are used for illumination as well as lightsensors for measuring ambient light in the location of the light fixture608. The lighting system 600 includes an ambient light module 612, alight fixture control module 616, a processor 620, and a communicationinterface 624. The communication interface 624 receives signals (e.g.,commands, clock source signals, trigger signals) from a light fixturecontrol system (e.g., light fixture control system 102 of FIG. 1).

The communication interface 624 conveys the signals to the processor620. The processor 620 (e.g., a microprocessor) communicates with andprovides commands to the ambient light module 612 and the light fixturecontrol module 616. For example, in normal operation, the light fixturecontrol module 616 turns on the light fixture 608 and provides a flow ofcurrent that travels through the LEDs 604 causing the LED 604 emittersto output light that is proportional to the current flow. LEDs have aset forward voltage (about 2.2V for red and amber LEDs, and about3.0-3.3V for white, blue and green LEDs).

In this embodiment, the processor 620 provides a trigger signal to theambient light module 612 and the light fixture control module 616 when aclock source signal (e.g., the clock source signal described withrespect to FIG. 1) is identified. In response to the clock sourcesignal, the processor 620 commands the light fixture control module 616to command the light fixture 608 to place the LEDs 604 in an off stateand therefore to stop outputting light and commands the ambient lightmodule to measure ambient light using the LEDs 604 of the light fixture.When these LEDs are in the off state, it is possible to measure thevoltage across the LEDs and correlate it to ambient light.

LED lighting fixtures typically contain 1 or more LED strings that aredriven with some method of control to provide illumination. When LEDsare turned “on”, there is a current travelling through the LED that hasa set forward voltage (about 2.2V for red and amber LEDs, and about3.0-3.3V for white, blue and green LEDs), illuminating light out of theemitter, proportional to the current flow. A common method forcontrolling LEDs is using Pulse Width Modulation (PWM). This is whereyou switch on and off the LEDs at a fixed period (frequency), and changethe duty cycle of on time to correspond to the desired intensity oflight emitted out of the LED.

LEDs are most commonly driven, using PWM (pulse width modulation). Inthis method, LEDs are digitally controlled via a square wave signal witha certain amount of on time (current being drawn thru the diode), and acertain amount of off time (no current flowing). When an LED fixture isbeing dimmed, the duty cycle will change such that the on time is less,and the off time more. From a human eyes standpoint, this isinstantaneous, as the human eye cannot notice this on/off time, but thelight source will appear dimmed to the human eye. Traditional fixturesin the same vicinity as an ambient light sensor can be either on or offwhen the ambient light sensor is taking its measurement. In the absenceof synchronization, the ambient light measurements may not be a truerepresentation of ambient light.

FIG. 6B is a graphical representation of different on and off periodsused for commanding the LEDs to be in the on-state and the off-state. Inthis example an arbitrary 10 us period is used as the fixed time forthat particular LED control. This can and will be variable, depending onthe implementation. As long as the frequency is fast enough the eyecannot detect the change from on to off or off to on. For a particularfixture the “on” time is displayed for 100%, 50% and 25% light output.In one embodiment, this is generally proportional to light intensity,except in this example 100% light output is 90% “on” as far as the dutycycle of the PWM. When a fixture is set to 25%, The LEDs are technically“off” 3 times as long as they are “on.” A person's eyes cannot updatefast enough to realize this so the cumulative effect makes the lightfixture to appear to be dim, rather than off for part of the time.Ultimately LEDs act as ambient light sensors when they are in the offstate, and they will produce a voltage across them proportional to theamount of light available. LEDs are typically in the off state for atleast a certain amount of time, even when outputting “full” intensity.

FIG. 6C is a schematic illustration of an LED string 604 in an exemplarysystem and how it is controlled by a switch (MOSFET) 608, viamicroprocessor control 612. The current setting resistors 616 at thebottom of FIG. 6C are used to set the current for the LED string.Measuring the voltage across the 6 LEDs when in the ON state, thevoltage will be a function of the sum of all the forward voltages of theLEDs in the string 604. For 6 White LEDs, this will be about 20V(3.3×6). In the off state (MOSFET 608 is switched off) this voltage willvary depending on the amount of natural light the LEDs see, which couldbe, for example, between 0-2V. This voltage will vary depending on thenumber of LEDs in the string 604 however, as it is the stack up, similarto the total forward voltage when on.

FIG. 6D shows a block diagram of one implementation capable of readingthis voltage (in the on or off state) with a microprocessor. Theimplementation involves reading the voltage of the rail (top of the LEDstring) and node between the last LED and the MOSFET (bottom of the LEDstring) with respect to ground, and computing the difference. The LEDstring voltage is equal to the difference between the A2D voltagereading 1 and A2D voltage reading 2. The rail voltage is resistordivided down to voltage read by the processor 612, but correlates to therail voltage. Block 670 is an AC/DC power supply. It will take a knownAC Voltage (e.g., 100V, 120V, 240V 277V) and convert it to a DC voltagerail (e.g., +24VDC, +15VDC, +12VDC) to drive the LEDs and associatedcontrol circuitry.

FIG. 6E illustrates a block diagram of an alternate embodiment thatenables the system to read the LED voltage. The embodiment in FIG. 6Duses a second MOSFET (the Pchannel MOSFET in this instance) to turn offthe rail voltage (24V) at the top of the LED string to completelyisolate the LED string while ambient light measurements are made usingthe LED string.

FIG. 7 is a block diagram of a clock source generator 700, according toan illustrative embodiment. The generator 700 is configured to generatea clock source signal that is used by a lighting system to synchronizelight fixtures in the system (e.g., the fixtures of FIGS. 1 and 3). Inthis embodiment, the generator 700 is configured to generate and outputa clock source signal 736 that can take the form of any one of fivedifferent protocols: zero-cross, power line communication, wireless,wired, and visual light communication. The power supply 704 of thegenerator 700 receives AC power, and the power supply 704 provides powerto the modules of the generator 700. The generator 700 also includes aprotocol converter 708 that converts an incoming control signal to asignal the synchronization module and generator 712 uses. A protocolconverter 708 could be a simple bridge between any one of the outputs(716, 720, 724, etc,) as an input control signal (into 708). It couldalso be something different, like a building automation protocol like,for example, BacNet (a data communication protocol for buildingautomation and control networks), or LonWorks (networking platformcreated to address the needs of control applications for, for example,lighting and HVAC).

The synchronization module and generator 712 generates the clock sourcesignal based on the control signal received from the protocol converter708. The clock source signal will be of the form needed for theparticular lighting system being used. For example, in some embodiments,the lighting system is configured such that zero-cross synchronizationis used, and therefore the synchronization module and generator 712would output a zero-cross signal to a zero-cross module 716. Thezero-cross module 716 would then output a clock source signal 736 in azero-cross format. The clock source signal 736 is provided tosynchronize the light fixtures (e.g., light fixtures 104 of FIG. 1), andas described herein with respect to, for example, the lighting system ofFIG. 1.

The clock source generator 700 also includes a PLC module 720, wirelessmodule 724, a wired module 728, and a visual light communication module732. The PLC module 720 outputs a clock source signal 736 in a PLCformat. The wireless module 724 outputs a clock source signal 736 in awireless format. The wired module 728 outputs a clock source signal 736in a wired format. The visual light communication module 732 outputs aclock source signal 736 in a visual light communication format.

Visual light communication (VLC) can be performed using, for example, acamera flash (e.g., a smart phone camera flash, or dedicated flash orlight source). VLC is a way of using the frequency spectrum that LEDsare controlled by, to use the light output from a fixture as a means tocommunication. This allows a smart phone to easily communicate with LEDlighting fixtures using VLC, without the need to use Wifi or other meshnetworking. In one implementation, the LED flash on a smart phone isequipped with internal circuitry in the phone to be able to use the LEDas a sensor and emitter for communication. In another implementation thescreen of the device is used to produce images on the LCD display tomimic the operation of the camera flash. In another implementation, adedicated light source in the lighting system is used to output theclock source signal 736.

FIG. 8A is block diagram of a lighting environment 800 that includes Nlight fixtures 804A, 804B . . . 804N (generally 804) and a lightingsystem commissioning system 808, according to an illustrativeembodiment. The system 808 includes a light fixture control module 812,an ambient light module 816, and a commissioning module 824. A lightsensor is assigned to each light fixture 804. In this embodiment, thelight fixtures 804 are LED light fixtures and the LEDs within the lightfixtures 804 are used both for illumination and for sensing ambientlight in proximity to the light fixtures 804. The LEDs are configuredfor illumination and sensing, similarly as described herein (e.g., withrespect to FIGS. 7A and 7C). FIG. 8B illustrates an alternativeembodiment, in which separate sensors 820A, 820B, . . . and 820N(generally 820) are included with the light fixtures 804 to measureambient light (rather than using the LEDs).

The light fixture control module 812 controls the operation of the lightfixtures 804. The ambient light module 816 is configured to measureambient light with the light sensor assigned to each light fixture 804.As described herein, in some embodiments it is desirable to commandlight fixtures to be in an off state when measuring ambient light in thelocation of the light fixtures. Accordingly, in some embodiments, thesystem 808 also includes a clock source generator (e.g., clock sourcegenerator 132 of FIG. 1), a monitoring module (e.g., monitoring module116 of FIG. 1), a triggering module (e.g., triggering module 120 of FIG.1), and a command module (e.g., command module 124 of FIG. 1). Thecombination of these modules is configured to synchronize the operationof the light fixtures 804 so the light fixtures 804 are not emittinglight when making ambient light measurements. The commissioning module824 is configured to designate each light fixture to a lighting group.The commissioning module 824 may, for example, designate light fixturesto particular lighting groups based on the ambient light measurements.

FIGS. 9A and 9B are schematic illustrations of light fixture groupingsof light fixtures 904A, 904B, 904C, 904D, 904E, and 904F (generally904), according to an illustrative embodiment. Referring to FIG. 9A,initially, one LED from each of the light fixtures 904 is configured tomeasure ambient light. Table 2 lists the light intensity measured usingLED1 of each of the light fixtures.

TABLE 2 Initial Ambient Light Measurement Light Intensity Light Fixture(Lumens) 904A 12 904B 10 904C 30 904D 15 904E 35 904F 40

The commissioning module 824 may group the light fixtures 904 based on avariety of different criteria. In this embodiment, the commissioningmodule 824 is configured to group fixtures based on the followingcriteria: Group 1 (light intensity <20 lumens); Group 2 (20 lumens≦lightintensity<40 lumens); Group 3 (light intensity ≧40 lumens). The purposefor grouping the light fixtures 904 is, in this embodiment, to creategroups of fixtures that are dimmed together during the course of theday. For example, because the light sensors for each fixture within agroup measured ambient light intensities that were relatively closelymatched, it might be desirable and beneficial to dim them in a similarmanner.

In some embodiments, after the light fixtures have been grouped, thecommissioning module 824 also specifies a single light sensor to be usedas a light sensor for determining how and/or when to dim the group oflight fixtures. For example, during the middle of the day it may bedesirable to dim a group of light fixtures in an area of a building thatget exposed to a considerable amount of natural light. Later in the day,as that group of light fixtures is exposed to less natural light, it maybe desirable to increase the output intensity of the light fixtures inthat group of light fixtures.

Referring to FIG. 9B, the system is configured to modify the grouping oflight fixtures. For example, it may be desirable to monitor ambientlight levels over the course of a period of time (e.g., month, year) todetermine how ambient light changes during that time period. If theambient light varies, the system may regroup the light fixtures. Table 3lists the light intensity measured using LED 1 of each of the lightfixtures at another point in time. Light fixtures 904A and 904D are inGroup 1, light fixtures 904E and 904F are in Group 2, and light fixtures904B and 904C are in Group 3.

TABLE 3 Subsequent Ambient Light Measurement Light Intensity LightFixture (Lumens) 904A 12 904B 42 904C 44 904D 15 904E 22 904F 30

There are many implementations where an LED can be used as a lightsensor. LEDs can be used as ambient light sensors in various lightfixture applications. Fixture electronics sense voltage differentials inthe LEDs that correlate to ambient light using the same LEDs that areused for illumination of the fixture. In one embodiment, the LED is usedas a light sensor for occupancy sensing; where the light measured by theLED varies if a subject is located in the field of view of the LED or ifa subject passes through the field of view. In some embodiments, the LEDis used as a light sensor to monitor or detect smoke/fog in, forexample, safety situations.

The technology described works with any type of LEDs (e.g., red, amber,green, blue, and white). The resolution of an LED as a light sensorchanges from LED to LED due to the specific characteristics of the LEDtype. For example, a red LED has a natural forward voltage of 2.2V, soresolution of ambient light will be different than other LEDs that haveforward voltage of 3V-3.3V (e.g., green, blue and white LEDs). Also,white LEDs have different characteristics than the colored LEDs becausea white LED has a phosphor coating over its royal blue die, which willblock some of the ambient light read by the LED. This is also true withfrosted lenses or diffusers that are sometimes used with LEDs. Theapplicable aspect of this however is that this only changes theresolution of the ambient sensor, as light will naturally get throughquite efficiently. For example, reading ambient light with a blue LEDmay give a voltage of 0V-2V depending on the amount of light available,where a white LED with phosphor may only yield a resolution of 0V-1.2V.The opposite is true for secondary optics that may be between the LEDsource and the ambient light. The focused optics will actually increasethe resolution of ambient light measured because it is focusing thelight in a particular direction (same thought as emitting light,receiving is through same optical properties).

In some embodiments, measurement and calibration techniques are appliedto LED fixtures in which one or more of the LEDs are used as lightsensors. One way to calibrate the LEDs involves using the off time inthe pulse width modulating (PWM) cycle of the LED illumination signaland measure the voltage across one or more of the LEDs when the LEDs arenon conducting (using them as sensors). In this implementation, theperiod and duty cycle of the signals can be adjusted such that when thefixture is at full output, the PWM signal is not at 100% duty cycle;allowing time available to measure the voltage of the LEDs when the LEDsemission signals are in the off state. There will be variation in thevoltage created by an LED and correlating to ambient light will beaffected depending on what type of LED, secondary optic, and/or lens isbeing used with an LED.

Calibration of the LEDs can be automatically done, or, alternatively usepredetermined calibration constants that are used or set atmanufacturing depending on specific fixture characteristics (i.e., if atight 6 degree or 10 degree secondary optic is used on the output of theLED, the resolution of the LED as a sensor will be greater than if thatsame LED had no secondary optic). LED performance as a sensor will varybased on other properties of the LED. For example, white LEDs functiondifferently than red, green, and blue LEDs because of the phosphormaterial used. This results in white LEDs having less resolution in thevoltage signal generated by the LED under the same ambient light levels.

When using an LED that is emitting light as a light sensor also, thereare many characteristics that need to be taken into account in order tocorrelate the ambient light measured to the ambient light in theenvironment that the fixture is in. These characteristics are variabledepending on the fixture system. The main variables associated withtrying use an LED from an LED fixture as ambient light are: forwardvoltage of the LED, voltage of reverse protection diode inside each LED,phosphor on the LED package, properties of secondary optics, andproperties of tertiary optics. FIG. 10 is a schematic illustration ofcomponents of an LED light fixture 1000 that is used to illustrate thedifferent components of a light fixture that affect its use as a sensor.The light fixture 1000 includes a printed circuit board (PCB) 1004 onwhich the components are mounted. The components are an LED die 1004,phosphor material 1012 for, for example, white LEDs, secondary optics1016, and tertiary optics/materials 1020.

LEDs of different technologies will vary in forward voltage. Forinstance, some red and amber colored LED dies 1008 are based on, forexample, Aluminum Gallium Arsenide (AlGaAs) technology, which leadstheir forward voltage to be in the 2.0V-2.2V range. Blue, White, andGreen LED dies 1008, however, use a different technology (e.g., IndiumGallium Nitride (InGaN) technology, and their forward voltage rangesfrom 2.8-3.5V. This different in voltage is a huge margin. This is evenmore significant when talking about the forward voltage differencesinside a particular yield of LEDs. Using white LEDs as an example, youcan see the variability in forward voltage can range upwards to 30%-35%.This is drastic, and hard to control in manufacturing. Therefore thisforward voltage needs to be measured and quantified.

Almost all high power LEDs used in lighting today have a reverseprotection diode in parallel to the LED inside the package. This diodeis usually a schottky diode, and voltage drop (in reverse direction fromnormal current path), will be anywhere from 0.2V-0.6V. This variabilityis important, because when using a high power LED as a sensor (by, forexample, reverse biasing the LED package by passing current thru it inthe opposite direction), the voltage drop of the schottky diode at thispoint will need to be taken into consideration to provide proper reversebias current.

Regarding white LEDs (and white emitting LED fixtures), there are twoother variables that combined play a significant role in measuringambient light. Since all white LEDs are only a royal blue LED with aphosphor coating 1012, the nm variation in the royal blue can have aneffect in the amount of light the LED can sense when used as a lightsensor. Most royal blue nanometer ranges for blue LEDs are in the450-460 nm range. Phosphor, however, has a huge effect on performance,depending on the amount of phosphor, or the type of phosphor. Phosphoris used to change the apparent color temperature or tint that aparticular LED may emit. This places a huge role in light detection whenbeing used as a light sensor. For example, more phosphor is used whentrying to turn the royal blue LED into a warm color temp of white, say2700K or 3000K, than a cooler LED, say 5700K or 6500K. This alsoexplains why cooler color temp LEDs are ultimately more efficient andemit more light, as there is less phosphor material applied 1012, andhence less light loss in transmission. The same principle applies whenconsidering light detection properties of the LED.

Many types of LED fixtures have, in addition to a lens on the physicalLED package, a secondary optics 1016 (e.g., lenses) to provideadditional focus and directionality of the light. These lenses can varyin beam width, shape and angle. The optics have an effect on thesensitivity and gain of the LED when used as a light sensor. Examplesinclude a conical 6 degree beam and an asymmetric 10 degree by 60 degreeprojection. When using the LEDs as sensors this will also affect theamount and angle of light incident on the LED. These factors need to beconsidered when correlating the expected ambient light over an areabased on the measured light on the LED through the optics.

The materials used to manufacture the focusing lenses will change theamount and spectra of any light that gets through to the LED. Glass,polycarbonate and other materials will act as filters and pass differentfrequencies of light depending on their material properties (e.g.,clear, frosted, diffuser coating, spread lens). Some lighting fixtureswill have an additional cover (e.g., tertiary optical elements) forphysical protection of the LED assemblies and in some cases it will alsoact as an additional diffusing lens. The material properties and amountof diffusion will affect the amount, directionality and spectra of theambient light that gets to the LEDs.

FIG. 11 is a schematic illustration of an LED light fixture calibrationsystem 1100, according to an illustrative embodiment. The calibrationsystem can be used to, for example, calibrate a light fixture based onthe properties/parameters described above with respect to FIG. 10. Thesystem 1100 includes a light source 1104 for generating a referencelight output 1108 for calibrating one or more LED light fixtures 112.The light source 1104 can be any controllable light source that outputslight (e.g., a traditional light fixture, incandescent light bulb, acalibrated piece of lab equipment). In this embodiment, the light source1104 is a controllable, calibrated light source that outputs multipleknown light levels. In alternative embodiments, a separate light sensorcan be used in conjunction with the system 1100 to measure the output ofthe light source 1104 during testing. The light source 1104 and LEDlight fixture 1112 are located within an enclosure 1120. The enclosure1120 prevents ambient light from impinging on the light source 1104 orLED light fixture 1112 during calibration. The enclosure 1120 thereforeenables the system 1100 to calibrate the LED light fixture 1112 in theabsence of ambient light.

During calibration, a power supply 1116 provides power to the LED lightfixture 1112 to operate the fixture. The system 1100 also includes acontrol system 1122. The control system 1122 includes a calibrationmodule 1124, a communication module 1132, one or more input devices1136, one or more output devices 1140, one or more display devices 1144,one or more processors 1148, and memory 1152. The modules and devicesdescribed herein can, for example, utilize the processor 1148 to executecomputer executable instructions and/or the modules and devicesdescribed herein can, for example, include their own processor toexecute computer executable instructions. It should be understood thecontrol system 1122 can include, for example, other modules, devices,and/or processors known in the art and/or varieties of the describedmodules, devices, and/or processors.

The calibration module 1124 performs various functions to calibrate theLED light fixture (as described, for example, with respect to FIG. 12).The communication module 1132 includes circuitry and code correspondingto computer instructions that enable the control system 1122 tosend/receive signals to/from, for example, the light source 1104 and LEDlight fixture 1112. For example, the communication module 1132 providescommands from the processor 1148 to the calibration module 1124 tocontrol how the light source 1104 transmits light within the enclosure1120 during operation. The communication module 1132 also, for example,receives data corresponding to the light measured by the LEDs in the LEDlight fixture 1112. The received data can be, for example, stored by thememory 1152 or otherwise processed by the processor 1148.

The input devices 1136 receive information from a user (not shown)and/or another computing system (not shown). The input devices 1136 caninclude, for example, a keyboard, a scanner, a microphone, a stylus, atouch sensitive pad or display. The output devices 1140 outputinformation associated with the control system 1122 (e.g., informationto a printer, information to a speaker, information to a display, forexample, graphical representations of information). The processor 1148executes the operating system and/or any other computer executableinstructions for the control system 1122 (e.g., executes applications).The memory 1152 stores a variety of information/data, including profilesused by the control system 1122 to specify how the system 1100calibrates a light fixture. The memory 1152 can include, for example,long-term storage, such as a hard drive, a tape storage device, or flashmemory; short-term storage, such as a random access memory, or agraphics memory; and/or any other type of computer readable storage.

FIG. 12 is a flowchart 1200 of a method for calibrating an LED lightfixture using, for example, the system 1100 of FIG. 11. The methodincludes placing the light source 1104 and the LED light fixture 1112into the enclosure 1120 (step 1204). By placing the light source 1104and the LED light fixture 1112 within the enclosure 1120, thecalibration steps can be performed in the absence of ambient light. Themethod also includes generating the reference light output 1108 from thelight source 1104 (step 1208). In some embodiments, the processor 1148executes instructions that cause the calibration module 1124 to commandthe light source 1104 to generate the reference light output 1108.

The method also includes measuring the reference light output 1108 fromthe light source 1104 by using one or more LEDs 1114 in the lightfixture 1112 as light sensors (step 1212). In some embodiments, each LEDof a plurality of LEDs in the LED light fixture 1112 acquires adifferent reference light output measurement. The calibration module1124 sends commands to the LED light fixture 1112 to cause the LEDs 1114to function as sensors (e.g., similarly as described herein). By usingthe LEDs in the light fixture 1112 as sensors, it is possible tocalibrate the light fixture to account for, for example, the variationin LED performance described above with respect to FIG. 10. Thisinvolves shining predetermined, fixed, various ambient light sources ofknown characteristics into the fixture, through all the variables listedabove. From there the fixture can automatically calibrate itself to thecorrect parameters and offsets, essentially teaching itself what are itsown variable characteristics.

The method then includes determining a calibration value (step 1216) bycomparing the reference light output measurement to a reference value.In this embodiment, the system 1100 acquires the reference value (step1220) from the memory 1152. In embodiments where multiple LEDs are used,the method involves determining a calibration value for each LED in theLED light fixture by comparing the reference light output measurement ofeach LED to a reference value.

In some embodiments, the reference values are stored in memory. Thesevalues are used in an equation as multipliers or gain values (i.e., ifan ambient light reading outside the fixture is a known number, say 100lux, and what is measure at the LED level is 35 lux, obviously there is65 lux that is lost through the different materials and processes of theLED fixture along the way. If you know the frosted lens is approximatelylux loss of 15 lux, plus the phosphor is a loss of 30 lux and thediffusion lens is a loss of 20 lux, that stack up is what amounts to thelosses seen. So the microprocessor will know that the 35 lux it isreading refers to 100 lux as a magnitude of scale. The next fixturebeing built might be without a diffuser, so the same 100 lux measurementcorresponds to 55 lux at the LED level, and the microprocessor knows thematerial offsets to calibrate for the different material stackups. Thesevalues will either be stored as individual values (i.e. 15%, +30%, +20%)for the system, or as one cumulative percentage value stored in onememory location, with the addition of the stackups done on the softwareside.

Application of the calibration value to the operation of the LED lightfixture 1112 causes the LED light fixture 1112 to operate havingproperties associated with the reference value (e.g., that allow the LEDlight fixture to be used to properly and accurately measure lightintensity, light color, light temperature, combinations of same). Asexplained above, the calibration values will be offsets associated withthe stackup of materials from the ambient light sources on the outsideof the fixture, through all the levels of loss (or gain in the case oftight optics) to where the light is capable of being read at the LEDlevel.

The method also includes storing the calibration value (step 1224) inmemory 1128 associated within the LED light fixture 1112. The storedcalibration value(s) can be, for example, accessed and used by a lightfixture control system when installing the LED light fixture 1112 in thefield.

FIG. 13 is a schematic illustration of an LED light fixture calibrationsystem 1300, according to an illustrative embodiment. In thisembodiment, the system 1300 is used to enter calibration constants intothe memory 1128 of an LED light fixture 1304 at manufacturing time.These constants tell the fixture what type of fixture it is as well asall of its characteristics detailed above in FIG. 10. The storedinformation is used during installation of the light fixture in order togive it the correct offsets to adjust the measured value to correlate toan actual value. In some embodiments, the system 1300 also can be usedby an operator to choose/specify the components that are known to beused within a specific light fixture. The operator can, for example, usean input device 1136 to specify the specific components within the LEDlight fixture 1304, so that nominal calibration constants (e.g., whiteLED with nominal forward voltage of 3.0 volts, 6 degree secondary optic,reverse current of 250 mA) can be stored within the memory 1128 of theLED light fixture.

Another implementation involves having each fixture be its own ambientlight sensor. The system then adjusts the light output of thecorresponding LED based on light level measured by the correspondingLED. This allows for maximum energy savings in the system because eachfixture can be automatically controlled and altered. Anotherimplementation involves having ambient light sensing available on everyfixture. However, when the light fixture is commissioned (e.g.,installed at the work site) the PLC is configured to enable only certainfixtures to serve as ambient light sensors for that particularinstallation, these ambient light readings will report back to acentralized control unit to control groups of fixtures all together. Insome implementations, a single LED is used to measure the ambient lightinstead of a string of LEDs. An advantage of using a string of LEDs isit increases the resolution of the ambient light measurement by addingup the sum of the LEDs in the string.

There are additional ways of figuring out that you are in the off statethat will give very accurate results. Since you can measure the voltagereal time, you will know when you are on (high voltage like 20V), andthen also when you are off, (0-2V). Based on your difference inmeasurements you can act accordingly. You also know the duty cycle ofyour PWM controlling your LEDs. So you have 2 methods of verificationthat the LEDs are in the “off” state. The second advantage is that, bydefault, since you are measuring the voltage when the LEDs are in theoff state, you are able to measure true ambient light, because thefixture is “off”, you are truly only measuring the ambient light aroundthe fixture.

With the ability to capture ambient light measurements on the fixtureitself, using power line communication one way to transfer/communicatethe ambient light data to other light fixtures, as well as a centralizedcontroller. This removes any need for outside communication withdaylight harvesting sensors. Since it is all part of the fixture in thisembodiment, it is embedded in the communications protocol as justanother piece of data that can be retrieved from fixtures. From there,calculations can be made about light fixtures and their surroundings,where every fixture could be its own light sensor and all fixtures inthe network can be averaged to get an ambient light level for a space.Alternatively, during commissioning, only a handful (or 1) fixture couldbe configured as the ambient light sensor for the group and all readingsand adjustments can be made based on that fixture's light readings.

Power line communication provides other advantages because system thatemploy PLC are able to report back to the system key diagnostic datasuch as temperature, power, LED lifetime, power supply lifetime, etc.

The above-described systems and methods can be implemented in digitalelectronic circuitry, in computer hardware, firmware, and/or software.The implementation can be as a computer program product. Theimplementation can be as a computer program product that is tangiblyembodied in non-transitory memory device. The implementation can, forexample, be in a machine-readable storage device and/or in a propagatedsignal, for execution by, or to control the operation of, dataprocessing apparatus. The implementation can, for example, be aprogrammable processor, a computer, and/or multiple computers.

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor receives instructions and data from a read-only memory or arandom access memory or both. The essential elements of a computer are aprocessor for executing instructions and one or more memory devices forstoring instructions and data. Generally, a computer can include, can beoperatively coupled to receive data from and/or transfer data to one ormore mass storage devices for storing data (e.g., magnetic,magneto-optical disks, or optical disks).

Data transmission and instructions can also occur over a communicationsnetwork. Information carriers suitable for embodying computer programinstructions and data include all forms of non-volatile memory,including by way of example semiconductor memory devices. Theinformation carriers can, for example, be EPROM, EEPROM, flash memorydevices, magnetic disks, internal hard disks, removable disks,magneto-optical disks, CD-ROM, and/or DVD-ROM disks. The processor andthe memory can be supplemented by, and/or incorporated in specialpurpose logic circuitry.

To provide for interaction with a user, the above described techniquescan be implemented on a computer having a display device. The displaydevice can, for example, be a cathode ray tube (CRT) and/or a liquidcrystal display (LCD) monitor. The interaction with a user can, forexample, be a display of information to the user and a keyboard and apointing device (e.g., a mouse or a trackball) by which the user canprovide input to the computer (e.g., interact with a user interfaceelement). Other kinds of devices can be used to provide for interactionwith a user. Other devices can, for example, be feedback provided to theuser in any form of sensory feedback (e.g., visual feedback, auditoryfeedback, or tactile feedback). Input from the user can, for example, bereceived in any form, including acoustic, speech, and/or tactile input.

The above described techniques can be implemented in a distributedcomputing system that includes a back-end component. The back-endcomponent can, for example, be a data server, a middleware component,and/or an application server. The above described techniques can beimplemented in a distributing computing system that includes a front-endcomponent. The front-end component can, for example, be a clientcomputer having a graphical user interface, a Web browser through whicha user can interact with an example implementation, and/or othergraphical user interfaces for a transmitting device. The components ofthe system can be interconnected by any form or medium of digital datacommunication (e.g., a communication network). Examples of communicationnetworks include a local area network (LAN), a wide area network (WAN),the Internet, wired networks, and/or wireless networks.

The system can include clients and servers. A client and a server aregenerally remote from each other and typically interact through acommunication network. The relationship of client and server arises byvirtue of computer programs running on the respective computers andhaving a client-server relationship to each other.

Transmitting devices can include, for example, a computer, a computerwith a browser device, a telephone, an IP phone, a mobile device (e.g.,cellular phone, personal digital assistant (PDA) device, laptopcomputer, electronic mail device), and/or other communication devices.The browser device includes, for example, a computer (e.g., desktopcomputer, laptop computer) with a world wide web browser (e.g.,Microsoft® Internet Explorer® available from Microsoft Corporation,Mozilla® Firefox available from Mozilla Corporation). The mobilecomputing device includes, for example, a Blackberry®.

Comprise, include, and/or plural forms of each are open ended andinclude the listed parts and can include additional parts that are notlisted. And/or is open ended and includes one or more of the listedparts and combinations of the listed parts.

One skilled in the art will realize the invention may be embodied inother specific forms without departing from the spirit or essentialcharacteristics thereof. The foregoing embodiments are therefore to beconsidered in all respects illustrative rather than limiting of theinvention described herein. Scope of the invention is thus indicated bythe appended claims, rather than by the foregoing description, and allchanges that come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed is:
 1. A method for controlling light emitting diode(LED) light fixtures, the method comprising: monitoring a clock sourcesignal to identify the presence of a feature in the clock source signal;generating a trigger signal with a triggering module in response toidentifying the presence of the feature in the clock source signal;providing the trigger signal to each of a plurality of light fixtures tocommand each of the plurality of light fixtures to stop outputtinglight; and measuring ambient light with a light sensor located with theplurality of light fixtures.
 2. The method of claim 1, wherein the clocksource signal is an alternating voltage signal, and wherein the featurein the clock source signal is the occurrence of a zero-crossing in thealternating voltage signal.
 3. The method of claim 1, wherein thetriggering commands each of the plurality of light fixtures to stopoutputting light for a predefined time period.
 4. The method of claim 1,wherein an ambient light monitor measures the ambient light in responseto the trigger signal.
 5. The method of claim 1, wherein the clocksource signal is: an AC or DC signal also used to provide power to theplurality of light fixtures; a power line communication signal carriedby an AC or DC signal used to provide power to the plurality of lightfixtures; or a signal transmitted by a clock source generator thatgenerates the clock source signal.
 6. The method of claim 1, wherein theambient light is measured using one or more light emitting diodes in theone or more of the plurality of light fixtures.
 7. The method of claim1, comprising varying operating parameters of one or more of the lightfixtures based on the measured ambient light.
 8. A light fixture controlsystem, the system comprising: a monitoring module that monitors a clocksource signal to identify the presence of a feature in the clock sourcesignal; a triggering module that generates a trigger signal in responseto identifying the presence of the feature in the clock source signal; acommand module that provides the trigger signal to each of a pluralityof light fixtures to command each of the plurality of light fixtures tostop outputting light; and a ambient light module that monitors ambientlight measured in proximity to the plurality of light fixtures.
 9. Thesystem of claim 8, wherein the clock source signal is an alternatingvoltage signal, and wherein the feature in the clock source signal isthe occurrence of a zero-crossing in the alternating voltage signal. 10.The system of claim 8, wherein the command module commands each of theplurality of light fixtures to stop outputting light for a predefinedtime period.
 11. The system of claim 8, wherein the ambient light modulemeasures the ambient light in response to the trigger signal.
 12. Thesystem of claim 8, wherein the clock source signal is: an AC or DCsignal also used to provide power to the plurality of light fixtures; apower line communication signal carried by an AC or DC signal used toprovide power to the plurality of light fixtures; or a signaltransmitted by a clock source generator that generates the clock sourcesignal.
 13. The system of claim 8, wherein the ambient light is measuredusing one or more light emitting diodes in the one or more of theplurality of light fixtures.
 14. The system of claim 8, wherein a lightfixture control module varies operating parameters of one or more of thelight fixtures based on the measured ambient light.
 15. A method forcommissioning a lighting system, the lighting system including aplurality of light fixtures, and a plurality of light sensors, where alight sensor from the plurality of light sensors is assigned to eachlight fixture, the method comprising: measuring ambient light with thelight sensor assigned to each light fixture; and designating each lightfixture to a lighting group based on the ambient light measured with thelight sensor assigned to each fixture.
 16. The method of claim 15,acquiring an updated measurement of ambient light with the light sensorsassigned to each light fixture and designating each light fixture to anew lighting group based on the updated ambient light measurements. 17.The method of claim 15, wherein the light sensors assigned to each lightfixture include one or more light emitting diodes in the light fixtureto measure the ambient light.
 18. The method of claim 15, wherein aunique light sensor is assigned to each light fixture.
 19. The method ofclaim 15, wherein a light sensor is assigned to more than one lightfixture.
 20. The method of claim 15, comprising prior to measuringambient light with the light sensor assigned to each light fixture,monitoring a clock source signal to identify the presence of a featurein the clock source signal; generating a trigger signal with atriggering module in response to identifying the presence of the featurein the clock source signal; providing the trigger signal to each of theplurality of light fixtures to command each of the plurality of lightfixtures to stop outputting light.
 21. The method of claim 15,comprising: making a plurality of measurements of ambient light over aperiod of time with the light sensor assigned to each fixture; modifyinglight fixture group designations based on the plurality of ambient lightmeasurements.
 22. The method of claim 15, comprising assigning one ormore of the light sensors to a different light fixture based on theambient light measurements.
 23. A lighting system commissioningapparatus, the lighting system including a plurality of light fixtures,and a plurality of light sensors, where a light sensor from theplurality of light sensors is assigned to each light fixture, theapparatus comprising: an ambient light module configured to measureambient light with the light sensor assigned to each light fixture; anda commissioning module configured to designate each light fixture to alighting group based on the ambient light measured with the light sensorassigned to each fixture.
 24. The apparatus of claim 23, wherein theambient light module is configured to acquire an updated measurement ofambient light with the light sensors assigned to each light fixture, andthe commissioning module is configured to designate each light fixtureto a new lighting group based on the updated ambient light measurements.25. The apparatus of claim 23, wherein the light sensors assigned toeach light fixture include one or more light emitting diodes in thelight fixture to measure the ambient light.
 26. The apparatus of claim23, wherein a unique light sensor is assigned to each light fixture. 27.The apparatus of claim 23, wherein a light sensor is assigned to morethan one light fixture.
 28. The apparatus of claim 23, comprising: amonitoring module; a triggering module; and a command module, whereinprior to measuring ambient light with the light sensor assigned to eachlight fixture, the monitoring module monitors a clock source signal toidentify the presence of a feature in the clock source signal, thetriggering module generates a trigger signal in response to identifyingthe presence of the feature in the clock source signal, and the commandmodule provides the trigger signal to each of a plurality of lightfixtures to command each of the plurality of light fixtures to stopoutputting light.
 29. A method for commissioning a lighting system, thelighting system including a plurality of light fixtures, the methodcomprising: measuring ambient light with a light sensor located with theplurality of light fixtures; and designating one or more of theplurality of light fixtures to a first lighting group based on themeasured ambient light.
 30. A method for grouping light fixture in alighting system; assigning a light sensor to each light fixture in thelighting system; measuring ambient light with the light sensor assignedto each light fixture over a period of time; and designating each lightfixture to a lighting group based on the ambient light measured with thelight sensor assigned to each fixture.
 31. A method for calibrating anLED light fixture, the method comprising: generating a reference lightoutput from a light source; measuring the reference light output fromthe light source by using at least one LED in the light fixture as alight sensor; determining a calibration value by comparing the referencelight output measurement to a reference value, such that by applicationof the calibration value to the operation of the LED light fixture, theLED light fixture will operate having properties associated with thereference value.
 32. The method of claim 31, comprising storing thecalibration value in a memory associated with the LED light fixture. 33.The method of claim 31, comprising placing the light source and LEDlight fixture in an enclosure and, in the absence of ambient light,generating the reference light output and measuring the reference lightoutput.
 34. The method of claim 31, wherein measuring the referencelight output from the light source includes measuring the referencelight output using the plurality of LEDs in the light fixture as lightsensors, wherein each LED of the plurality of LEDs acquires a differentreference light output measurement.
 35. The method of claim 34,comprising determining a calibration value for each LED in the LED lightfixture by comparing the reference light output measurement of each LEDto a reference value.
 36. The method of claim 35, comprising storingeach LED's calibration value in a memory associated with the LED lightfixture.
 37. The method of claim 31, wherein, by application of thecalibration value to the operation of the LED light fixture, the LEDlight fixture will sense light having properties associated with thereference value.
 38. The method of claim 31, wherein measuring thereference light output from the light source includes measuring thereference light output using the plurality of LEDs in the light fixtureas light sensors, wherein the plurality of LEDs is configured as astring of LEDS to acquire the light output measurement.
 39. An LED lightfixture calibration system, the system comprising: a light source togenerate a reference light output; and a calibration module coupled tothe light source and an LED light fixture, wherein the calibrationmodule measures the reference light output from the light source byusing at least one LED in the light fixture as a light sensor and,wherein the calibration module determines a calibration value bycomparing the reference light output measurement to a reference value,such that by application of the calibration value to the operation ofthe LED light fixture, the LED light fixture will operate havingproperties associated with the reference value.
 40. The system of claim39, comprising a processor for storing the calibration value in a memoryassociated with the LED light fixture.
 41. The system of claim 39,comprising an enclosure in which the light source and LED light fixtureare placed and, in the absence of ambient light, the light sourcegenerates the reference light output and the LED light fixture measuresthe reference light output.
 42. The system of claim 39, wherein the LEDlight fixture has a plurality of LEDS and the LEDs measure the referencelight output using the plurality of LEDs in the light fixture as lightsensors, wherein each LED of the plurality of LEDs acquires a differentreference light output measurement.
 43. The system of claim 42, whereinthe calibration module determines a calibration value for each LED inthe LED light fixture by comparing the reference light outputmeasurement of each LED to a reference value.
 44. The system of claim43, wherein the processor stores each LED's calibration value in amemory associated with the LED light fixture.
 45. The system of claim39, wherein, by application of the calibration value to the operation ofthe LED light fixture, the LED light fixture will sense light havingproperties associated with the reference value.
 46. The system of claim39, wherein measuring the reference light output from the light sourceincludes measuring the reference light output using the plurality ofLEDs in the light fixture as light sensors, wherein the plurality ofLEDs is configured as a string of LEDS to acquire the light outputmeasurement.